In an internal combustion engine, an engine running speed is often varied due to the changes of output loads. One of the goals is to maintain a constant engine speed during the change of the load. Another goal is to adjust an engine speed when it is desired. The speed adjustment allows lower speed operation at light engine loads and higher speed operation at greater engine loads. Thus, a quiet operation with a light engine horsepower demand is allowed.
To achieve these goals, an electrically controlled actuator is often used to maintain the engine speed or adjust the engine speed via regulating the amount of the engine combustion fluid, such as air/fuel mixture. An electrical control current is sent to an electrically controlled actuator which converts the electrical control current to magnetic torques so as to actuate the electrically controlled actuator. The actuator then regulates the ratio of fuel/air mixture in a carburetor, or regulates the amount of air in a throttle body, or controls the amount of fluid in the other types of fluid flow metering devices. The change of the fuel/air mixture ratio or the change of the amount of air causes the engine to maintain its running speed or adjust its running speed.
The electrical control current sent to the actuator is usually generated by a microprocessor or digital/analog control methods. The microprocessor generates the electrical control current according to an output of an engine speed sensor. The sensed signal is sent to the microprocessor where calculations are made to correct errors of the air/fuel mixture ratio of a carburetor, or errors of the air amount of a throttle body, or errors of the fluid amount of the other types of fluid flow metering devices. The errors are used to determine whether the electrical control current sent to the actuator should be raised or lowered. Then, the electrical control current, with the result of the calculations and determination, is generated by the microprocessor and sent to the actuator.
Various rotary electrically actuated devices for regulating fluid flow, such as air/fuel mixture or pure air, have been provided in the art. These electrically actuated devices receive an electrically control current determined from various engine operating parameters and act like a valve regulating the fluid flow supplied to the engine. Oftentimes, these devices are complicated in structure which includes a lot of components and is often difficult to manufacture. As a result, these devices are often very expensive. In addition, due to the complexity of the structure, performances of the device are often not very satisfied. One of the main performances is to maximize a rotating range of a fluid flow plate while minimizing the package size of the actuator, so that the regulating range of the actuator is maximized while minimizing the package size of the actuator. The physical size of the conventional devices which can obtain the same angular displacement is often about two times of the physical size of the present invention. Another performance is to linearize the current-load curve, the input-output curve of the fluid flow metering system. The current-load curve characterizes the regulation performance of the actuator. The more linear the curve is, the better the regulation of the fluid flow is. The current-load curve of these conventional devices is not linear so that the regulation performance is not very satisfied.
Therefore, there is a need for an electrically controlled actuator which has a simple structure thus less expensive and has better performance with ensured durability and reliability.